Catecholamines, including dopamine (DA), norepinephrine (NE) and epinephrine (EPI) and their metabolites and dopamine-beta-hydroxylase are determined in plasma and cerebrospinal fluid (CSF). Levels of the NE in plasma reflect sympathetic neuronal activity while levels of EPI reflect adrenal medullary secretion. Increases in NE normally elicited by standing and by exertion provide a useful index of sympathetic function and this test is used to study the role of the sympathetics in hypertension, orthostatic hypotension of various types, and the effects of psychoactive drugs. Amines are present in CSF, and their levels vary during the day. Amines in CSF may provide a means of studying drug effects on brain amine metabolism. BIBLIOGRAPHIC REFERENCES: Lake, C.R., Ziegler, M.G., Coleman, M.D., and Kopin, I.J.: Age-adjusted plasma norepinephrine levels are similar in normotensive and hypertensive subjects. N. Engl. J. Med. 296: 208-209, 1977. Ziegler, M.G., Lake, C.R., and Kopin, I.J.: The sympathetic nervous system defect in primary orthostatic hypotension. N. Engl. J. Med. 296: 293-297, 1977.